Solid-state Chemical Reduction Research Articles

Photothermal-Enhanced Fenton-like Catalytic Activity of Oxygen-Deficient Nanotitania for Efficient and Safe Tooth Whitening.

The growing demand for charming smiles has led to the popularization of tooth bleaching procedures. Current tooth bleaching products with high-concentration hydrogen peroxide (HP, 30-40%) are effective but detrimental due to the increased risk of enamel destruction, tooth sensitivity, and gingival irritation. Herein, we reported a less-destructive and efficient tooth whitening strategy with a low-concentration HP, which was realized by the remarkably enhanced Fenton-like catalytic activity of oxygen-deficient TiO2 (TiO2-x). TiO2-x nanoparticles were synthesized with a modified solid-state chemical reduction approach with NaBH4. The Fenton-like activity of TiO2-x was optimized by manipulating oxygen vacancy (OV) concentration and further promoted by the near-infrared (NIR)-induced photothermal effect of TiO2-x. The TiO2-x sample named BT45 was chosen due to the highest methylene blue (MB) adsorption ability and Fenton-like activity among acquired samples. The photothermal property of BT45 under 808 nm NIR irradiation was verified and its enhancement on Fenton-like activity was also studied. The BT45/HP + NIR group performed significantly better in tooth whitening than the HP + NIR group on various discolored teeth (stained by Orange II, tea, or rhodamine B). Excitingly, the same tooth whitening performance as the Opalescence Boost, a tooth bleaching product containing 40% HP, was obtained by a self-produced bleaching gel based on this novel system containing 12% HP. Besides, negligible enamel destruction, safe temperature range, and good cytocompatibility of TiO2-x nanoparticles also demonstrated the safety of this tooth bleaching strategy. This work indicated that the photothermal-enhanced Fenton-like performance of the TiO2-x-based system is highly promising in tooth bleaching application and can also be extended to other biomedical applications.

In situ synthesis of an advanced Z-scheme Bi/BiOI/black TiO2 heterojunction photocatalysts for efficient visible-light-driven NO purification

Limited light absorption and severe charge recombination have been widely acknowledged as the two main obstacles restricting the application of P25 in NO photocatalytic conversion. In this work, an advanced heterojunction photocatalyst of Bi/BiOI/black TiO2 was synthesized via an in-situ solid-state chemical reduction method. The black TiO2 extended the light absorption to the full spectral region. It constructed a direct Z-scheme heterojunction with BiOI nanosheets, not only promoting the charge separation, but also preserving the strong oxidation ability of photogenerated holes in black TiO2 and strong reducing ability of photogenerated electrons in BiOI. Thus, more •O2− and •OH radical could form when Bi/BiOI/black TiO2 was subjected to visible light irradiation. Besides, the introduced Bi metal nanoparticles could also enhance the light utilization and served as a cocatalyst to accept the electrons. Therefore, enhanced NO photocatalytic oxidation activity was obtained, with the optimal sample Bi/BiOI/black TiO2 exhibiting a high NO conversion efficiency of ~70% and NOx removal of ~45%. This work may provide a refreshing perspective for the design of heterojunction photocatalysts for efficient NO photocatalytic purification and other photocatalytic applications.

Green Solid-State Chemical Reduction of Graphene Oxide Supported on a Paper Substrate

The reduction of graphene oxide (GO) thin films deposited on substrates is crucial to achieve a technologically useful supported graphene material. However, the well-known thermal reduction process cannot be used with thermally unstable substrates (e.g., plastics and paper), in addition photo-reduction methods are expensive and only capable of reducing the external surface. Therefore, solid-state chemical reduction techniques could become a convenient approach for the full thickness reduction of the GO layers supported on thermally unstable substrates. Here, a novel experimental procedure for quantitative reduction of GO films on paper by a green and low-cost chemical reductant (L-ascorbic acid, L-aa) is proposed. The possibility to have an effective mass transport of the reductant inside the swelled GO solid (gel-phase) deposit was ensured by spraying a reductant solution on the GO film and allowing it to reflux in a closed microenvironment at 50 °C. The GO conversion degree to reduced graphene oxide (r-GO) was evaluated by Fourier transform infrared spectroscopy (FT-IR) in attenuated total reflectance (ATR) mode and X-ray Diffraction (XRD). In addition, morphology and wettability of GO deposits, before and after reduction, were confirmed by digital USB microscopy, scanning electron microscopy (SEM), and contact angle measurements. According to these structural characterizations, the proposed method allows a bulky reduction of the coating but leaves to a GO layer at the interface, that is essential for a good coating-substrate adhesion and this special characteristic is useful for industrial exploitation of the material.

Plasmon-enhanced broad-band quantum-cutting of NaBaPO4:Eu2+,Er3+ phosphors with silver nano-particles

NaBaPO4:Eu2+,Er3+ phosphors and Ag nano-particles (NPs) were prepared by the solid-state reaction and chemical reduction method, respectively. The fluorescence spectra and decay curves demonstrate the effective energy transfer from Eu2+ to Er3+ and the existence of three-photon quantum-cutting through two-step cross-relaxation of Er3+. The quantum-cutting emission is peaked at 1534 nm with a broad excitation band centered at 352 nm. Plasmon-enhanced quantum-cutting of NaBaPO4:Eu2+,Er3+ phosphors was realized by decorating Ag NPs. The largest enhancement factor is 1.395. It is hopeful to improve the photovoltaic conversion efficiency of Ge solar cells by using this phosphor.

Synergism of oxygen vacancies, Ti3+ and N dopants on the visible-light photocatalytic activity of N-doped TiO2

N-doped TiO2 photocatalyst with abundant oxygen vacancies (N-TiO2-x) has been fabricated by a novel solvothermal route (using HNO3 as a nitrogen source) combined with a solid-state chemical reduction method for the first time. Using this combined technology, high-quality N-TiO2-x photocatalyst with small mean particle size (around 7.1 nm) and high surface area (181.7 m2/g) can be acquired. The electron paramagnetic resonance and X-ray photoelectron spectrometer results indicate that oxygen vacancy and Ti3+ are produced in N-TiO2-x during solid-state chemical reduction process. Control experiments show that compare to pristine N-doped TiO2 and pure TiO2, the reduction activated N-TiO2-x catalyst has a great improvement in both optical absorption and photocatalytic performance. It suggests that the N-TiO2-x band-gap narrowing results from synergetic effect of Ti3+ and oxygen vacancies defect energy state belts, as well as N2p midgap state. These energy levels result in enhanced visible light absorption and serve to trap the photogenerated electrons, consequently improving both charge separation and the quantum efficiencies of N-TiO2-x catalysts.

Surface plasma Ag-decorated single-crystalline TiO2−x(B) nanorod/defect-rich g-C3N4 nanosheet ternary superstructure 3D heterojunctions as enhanced visible-light-driven photocatalyst

Ag-TiO2−x(B)/g-C3N4 ternary heterojunctions photocatalysts are fabricated by hydrothermal-calcination, photo-deposition procedure, and followed by in-situ solid-state chemical reduction procedure. As-obtained photocatalysts are consisted with heterojunctions between 2D g-C3N4 sheets and 1D TiO2(B) single-crystalline nanorods. The band gap of Ag-TiO2−x(B)/g-C3N4 ternary heterojunctions photocatalysts is reduced to ∼2.23 eV due to plasma Ag and surface engineering. Under visible light irradiation, it has an optimal photocatalytic property for the reduction of Cr6+ (95%) and degradation of NH4+ (93%). The apparent reaction rate constants (k) of ternary heterojunctions photocatalysts for NH4+ and Cr6+ are 25 and 12 folds higher than that of original TiO2(B). Furthermore, Ag-TiO2−x(B)/g-C3N4 also has excellent hydrogen production efficiency, which is up to 410 µmol h−1 g−1. This enhancement can be attributed to the unique heterojunction formed by 1D single-crystalline TiO2(B) nanorods and 2D g-C3N4 sheets, surface plasma resonance effect of plasma Ag nanoparticle, and surface engineering. A possible photocatalytic mechanism is also proposed by analysizing the XPS valence-band spectra and the Mott-Schottky.

Surface defect and rational design of TiO2−x nanobelts/ g-C3N4 nanosheets/ CdS quantum dots hierarchical structure for enhanced visible-light-driven photocatalysis

TiO2-x/g-C3N4/CdS ternary heterojunctions are fabricated through thermal polymerization-chemical bath deposition combined with in-situ solid-state chemical reduction approach. The prepared materials are characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and X-ray photoelectron spectroscopy. The results show that the ternary heterojunctions are formed successfully and CdS quantum dots (QDs) and TiO2 are anchored on surface of g-C3N4 nanosheets simultaneously. The visible-light-driven photocatalytic degradation ratio of Bisphenol A and hydrogen production rate are up to 95% and ∼254.8 μmol h−1, respectively, which are several times higher than that of pristine TiO2. The excellent visible-light-driven photocatalytic activity can be ascribed to the synergistic effect of TiO2−x, g-C3N4 and CdS QDs which extend the photoresponse to visible light region and favor the spatial separation of photogenerated charge carriers.

Assembly of surface-defect single-crystalline strontium titanate nanocubes acting as molecular bricks onto surface-defect single-crystalline titanium dioxide (B) nanorods for efficient visible-light-driven photocatalytic performance

Ti3+ self-doped single-crystalline SrTiO3−x nanocubes acting as molecular bricks are successfully assembled onto Ti3+ self-doping single-crystalline TiO2−x(B) nanorods through an effortless two-step hydrothermal process coupled with an in situ solid-state chemical reduction method. SrTiO3−x nanocubes act as molecular bricks, which are uniformly assembled onto the surface of TiO2−x(B) nanorods due to lattice matching. The band gap of the resultant SrTiO3−x/TiO2−x(B) sample is ∼2.97 eV, which exhibits excellent photocatalytic performance for the reduction of Cr(VI) and hydrogen production under visible light. The apparent rate constant k value for the photocatalytic reaction of SrTiO3−x/TiO2−x(B) for Cr(VI) reduction is ∼8 times higher than that of white TiO2(B). The photocatalytic hydrogen production rate for SrTiO3−x/TiO2−x(B) is ∼160.2 μmol g−1 h−1, which is ∼5 times higher than that of white TiO2(B). The enhanced photocatalytic activity can be considered to be caused by a synergetic effect of heterojunction formation and the introduction of Ti3+ self-doping, which can not only facilitate the separation of photogenerated charge carriers between TiO2−x(B) and SrTiO3−x, but also broaden the photoresponse from the UV to visible-light region.

Synthesis of Self-Gravity Settling Faceted-Anatase TiO2 with Dominant {010} Facets for the Photocatalytic Degradation of Acetaminophen and Study of the Type of Generated Oxygen Vacancy in Faceted-TiO2

In this study, faceted TiO2, predominately exposed with {010} facets (T-{010}), was synthesized with a two-step hydrothermal reaction and used for the degradation of acetaminophen (ACE) in an aqueous solution. T-{010} showed considerable photocatalytic reactivity, and its easy-settling (gravity-settling, ~97% of T-{010} settled after 30 min) property demonstrated acceptable reusability. A solid-state chemical reduction approach (NaBH4) at a mild temperature (300 °C) was used for generation of an oxygen vacancy in T-{010} and P25 (commercial TiO2). The oxygen vacancy concentrations of the samples were investigated by electron paramagnetic resonance (EPR). It was also found that NaBH4 reduction induced the generation of both surface and subsurface Ti3+ on colored P25, but only surface Ti3+ species were formed on colored T-{010}. The prepared colored TiO2 samples were successfully used for photocatalytic degradation of ACE in an aqueous solution under visible light illumination.

Synergistic effect of surface plasmon resonance, Ti3+ and oxygen vacancy defects on Ag/MoS2/TiO2-x ternary heterojunctions with enhancing photothermal catalysis for low-temperature wastewater degradation.

Ag/MoS2/TiO2-x ternary heterojunctions are fabricated through hydrothermal and photo-deposition process combine with in-situ solid-state chemical reduction approach. The prepared materials are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, and X-ray photoelectron spectroscopy. The results show that the ternary heterojunctions doped with Ti3+ are formed, meanwhile, Ag nanoparticle and MoS2 nanosheets are anchored on surface of TiO2 nanobelts simultaneously. The photocatalytic degradation ratio of Bisphenol A in low temperature water and hydrogen production rate for Ag/MoS2/TiO2-x are up to 96.7% and ∼1.98 mmol h-1 g-1, respectively, which are several times higher than that of pristine TiO2. Furthermore, the photothermal performance of Ag/MoS2/TiO2-x is also unexpected. The excellent photocatalytic activity and photothermal performance can be ascribed to the synergistic effect of the formation of heterojunctions, Ti3+ and surface oxygen vacancies defects and surface plasmon resonance of Ag nanoparticles, which extend the photoresponse to visible-infrared light region and favor the spatial separation of photogenerated charge carriers.

A solid-state chemical reduction approach to synthesize graphitic carbon nitride with tunable nitrogen defects for efficient visible-light photocatalytic hydrogen evolution

Graphitic carbon nitride with nitrogen defects (g-C3N4-x) is prepared by a facile and effective solid-state chemical reduction technique at mild temperature conditions. The cyano groups and nitrogen vacancies, as evidenced by electron paramagnetic resonance (EPR), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectra (FTIR) and Solid-state 13C MAS NMR spectra, are controllable via adjusting chemical reduction temperature. Comparing to the pristine g-C3N4, the as-prepared g-C3N4-x shows much enhanced photocatalytic H2 evolution activity under visible-light irradiation. The maximum H2 evolution rate of 3068 μmol·g−1·h−1 is achieved with g-C3N4-x after chemical reduction treatment at 400 °C for 1 h, which is 4.85 times that of the pristine g-C3N4. Moreover, excellent reusability and storage stability have been shown by this photocatalyst as well. It is discovered that nitrogen defects can result in both the up-shift of the valance band and the down-shift of the conduction band, which benefit the absorption of longer wavelength photons and trapping of the photoinduced electrons, therefore reducing the recombination losses of the generated carriers. It is because of this improved visible-light absorption and charge carrier separation, g-C3N4-x displays better visible-light photocatalytic activity compared to the pristine g-C3N4. It is then concluded that the synthetic strategy presented here represents a straightforward and efficient way to synergistically optimize the chemical composition, optical response, and photocatalytic characteristics of g-C3N4-based photocatalysts.

In-situ N-doped mesoporous black TiO2 with enhanced visible-light-driven photocatalytic performance

In-situ N-doped mesoporous black TiO2 photocatalyst is fabricated by a facile sol-gel method combined with an in-situ solid-state chemical reduction technique, using urea as nitrogen resource. The N-doped mesoporous black TiO2 possesses high surface area of 96 m2 g−1, large pore size of 5.4 nm and narrow band gap of 2.05 eV. Meanwhile, the optical absorption extends to visible light region because of Ti3+ and N co-doping. The N-doped mesoporous black TiO2 exhibits higher photocatalytic activity than that of others under visible light irradiation for photocatalytic degradation of methyl orange (MO) and rhodamine B (RhB), which is up to 93.27% and 93.64%, respectively. The enhancement is ascribed to the synergistic effect of the N and Ti3+ co-doping extending the visible light absorption, the separation efficiency of photogenerated charge carriers, and the mesoporous structure with large surface area offering more surface active sites, which is beneficial for improving the photocatalytic activity.

Ti3+ self-doped rutile/anatase/TiO2(B) mixed-crystal tri-phase heterojunctions as effective visible-light-driven photocatalysts

Ti3+ self-doped rutile/anatase/TiO2(B) mixed-crystal tri-phase heterojunctions photocatalysts are fabricated via hydrothermal approach and mechanochemical process, followed by in-situ solid-state chemical reduction approach. The as-prepared samples are characterized by X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalysts are consisted by anatase/rutile TiO2 nanoparticles and 1D TiO2(B) single-crystalline nanorods, which form rutile/anatase/TiO2(B) tri-phase heterojunctions. The visible-light-driven photocatalytic degradation rates of methyl orange and phenol are up to ∼98 and 97%, which are 2.2 and 1.8 times higher than that of commercial Degussa P25, 2.3 and 2.2 times higher than that of pure TiO2(B) as well. The enhancement can be attributed to the synergistic effect of special nanostructure, tri-phase heterojunctions, oxygen vacancy and Ti3+ self-doping, which facilitates the absorption of visible light and the spatial separation of photo-generated charge carriers. This work provides a new perspective for designing high-active visible-light-driven photocatalyst in future.

Charge Carrier Dynamics in TiO2 Mesocrystals with Oxygen Vacancies for Photocatalytic Hydrogen Generation under Solar Light Irradiation

There is a great concern about black TiO2 prepared by H2 treatment because of its ability to enhance light harvesting of TiO2. Black TiO2 shows different photocatalytic activities compared with white TiO2. However, the mechanism of photocatalytic reaction has not been clearly understood. Here, femtosecond time-resolved diffuse reflectance (fs-TRDR) spectroscopy and single-particle photoluminescence measurements were applied to gain better understanding about the relation between oxygen vacancy, charge transfer, lifetime of photogenerated charge, and photocatalytic activity. We prepared reduced TiO2 mesocrystals (R-TMC) through simple solid-state chemical reduction at moderate temperature 350 °C. R-TMC has nearly two times higher photocatalytic activity for H2 production under solar light irradiation. The presence of oxygen vacancies and Ti3+ was studied by electro paramagnetic resonance and X-ray photoelectron spectroscopy. This work confirms the findings of previous studies that enhancement of light abso...

A Facile Method for the Preparation of Colored Bi₄Ti₃O12-x Nanosheets with Enhanced Visible-Light Photocatalytic Hydrogen Evolution Activity.

Bi4Ti3O12−x nanosheet photocatalysts with abundant oxygen vacancies are fabricated by a facile solid-state chemical reduction method for the first time. This method is simple in operation, has short reaction time, and can be conducted at mild temperatures (300~400 °C). The electron paramagnetic resonance, thermogravimetric analysis, X-ray photoelectron spectrometer, and positron annihilation lifetime spectra results indicate that oxygen vacancies are produced in Bi4Ti3O12−x, and they can be adjusted by tuning the reduction reaction conditions. Control experiments show that the reduction time and temperature have great influences on the photocatalytic activities of Bi4Ti3O12−x. The optimal Bi4Ti3O12−x is the sample undergoing the reduction treatment at 350 °C for 60 min and it affords a hydrogen evolution rate of 129 μmol·g−1·h−1 under visible-light irradiation, which is about 3.4 times that of the pristine Bi4Ti3O12. The Bi4Ti3O12−x photocatalysts have good reusability and storage stability and can be used to decompose formaldehyde and formic acid for hydrogen production. The surface oxygen vacancies states result in the broadening of the valence band and the narrowing of the band gap. Such energy level structure variation helps promote the separation of photo-generated electron-hole pairs thus leading to enhancement in the visible-light photocatalytic hydrogen evolution. Meanwhile, the narrowing of the band gap leads to a broader visible light absorption of Bi4Ti3O12−x.

Bi plasmon-enhanced mesoporous Bi2MoO6/Ti3+ self-doped TiO2 microsphere heterojunctions as efficient visible-light-driven photocatalysts

Bi plasmon-enhanced mesoporous Bi2MoO6/Ti3+ self-doped TiO2 microsphere heterojunctions (Bi-BMO/TiO2-x) have been synthesized by a mild hydrothermal method combined with an in situ solid-state chemical reduction process, and subsequently annealed at 400 °C in N2 atmosphere. The prepared Bi-BMO/TiO2-x photocatalysts are characterized by X-ray diffraction, N2 adsorption, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results reveal that Ti3+ self-doped TiO2 is loaded on surface of mesoporous Bi2MoO6 microsphere efficiently and metallic Bi is produced for surface plasmon resonance (SPR). Under visible-light irradiation, the heterojunctions photocatalyst shows excellent photodegradation and photoelectrochemical properties of ∼95% for phenol removal rate and 20 μA/cm2 for photocurrent density, respectively, which is several times higher than that of single component. Moreover, it also has high photocatalytic oxygen production with a rate of 134 μmol h-1 g-1. The enhanced photocatalytic activities are mainly attributed to the existence of Ti3+ self-doping and heterojunction structure, which narrow the band gap to extend photoresponse to visible light region. Another reason is the influence of SPR of metallic Bi. They all promote the spatial separation and transfer of photogenerated charge carriers.

CdS quantum dots/Ti3+-TiO2 nanobelts heterojunctions as efficient visible-light-driven photocatalysts

CdS quantum dots (QDs)/Ti3+-TiO2 nanobelts heterojunctions as 0D/1D architectures are fabricated through hydrothermal-chemical bath deposition combine with in-situ solid-state chemical reduction approach. The CdS QDs of ∼7 nm are loaded on TiO2 nanobelts with width of 50–300 nm and several micrometers long, and the heterojunctions are formed efficiently. The prepared heterojunctions exhibit excellent photocatalytic performance for complete removal of methylene blue (∼99%) and hydrogen production efficiency (∼480.6 μmol h−1) under visible light irradiation, which are as high as 2 and 23 times than that of pristine TiO2 nanobelts. The enhancement is attributed to the Ti3+ self-doping and CdS QDs extend the photoresponse to visible light region and the formation of heterojunctions favor the spatial separation of photogenerated charge carriers. Therefore, the high-efficient 0D/1D heterojunction composites have potential applications in the field of environment and energy.

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

Oxygen vacancy (VO) plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO (0–2.18%) are fabricated via an in-situ solid-state chemical reduction strategy, with color from white to black. The bandgap of the resultant rutile TiO2 is reduced from 3.0 to 2.56 eV, indicating the enhanced visible light absorption. The resultant rutile TiO2 with optimal contents of VO (~2.07%) exhibits a high solar-driven photocatalytic hydrogen production rate of 734 μmol h−1, which is about four times as high as that of the pristine one (185 μmol h−1). The presence of VO elevates the apparent Fermi level of rutile TiO2 and promotes the efficient electron-hole separation obviously, which favor the escape of photogenerated electrons and prolong the life-time (7.6×103 ns) of photogenerated charge carriers, confirmed by scanning Kelvin probe microscopy, surface photovoltage spectroscopy and transient-state fluorescence. VO-mediated efficient photogenerated electron-hole separation strategy may provide new insight for fabricating other high-performance semiconductor oxide photocatalysts.

Ti3+-TiO2/Ce3+-CeO2 Nanosheet heterojunctions as efficient visible-light-driven photocatalysts

Novel Ti3+-TiO2/Ce3+-CeO2 nanosheet heterojunctions are successfully prepared via a facile hydrothermal approach combined with a wet-chemical deposition precipitation and an in situ solid-state chemical reduction strategy. The structures of the as-prepared samples are characterized in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. The results show that Ti3+ and Ce3+ are both doped into the lattice of TiO2 and CeO2, respectively, which narrow the band gap to 2.7 eV and extend the photoresponse to visible light region. The photocatalytic degradation rate of methyl orange and methylene blue are as high as 93.3% and 97.1% under visible-light illumination, respectively. The high degradation rate is attributed to the efficient doping of Ti3+ and Ce3+, formation of surface oxygen vacancy and heterojunction, which favors the absorption of visible light and separation of photogenerated charge carriers.

Surface plasmon resonance-enhanced visible-light-driven photocatalysis by Ag nanoparticles decorated S-TiO2− nanorods

Abstract A novel plasmonic Ag decorated S-TiO2−x nanorods are successfully fabricated under 700 °C calcination, then followed by an in-situ solid-state chemical reduction approach with NaBH4 in a mild calcination (350 °C) and combined with photo-deposition approach. The resultant Ag/S-TiO2−x sample with high crystallinity and narrow band gap of ∼2.39 eV, extends the photoresponse to near-infrared region. The visible-light-driven photocatalytic degradation rate of phenol and hydrogen production rate for Ag/S-TiO2−x nanorods are as high as 98.67% and 209.2 µmol h−1 g−1, which is about 2 and 5 times higher than that of S-TiO2. Especially, first-order reaction rate constant of Ag/S-TiO2−x nanorods is 14 times higher than that of S-TiO2. The excellent photocatalytic property can be attributed to the synergistic effect of Ti3+ self-doping, S doping and the enhanced surface plasmon resonance of Ag nanoparticles, which narrows the band gap, favors the visible light utilization, and promotes the separation of photogenerated charge carriers.